The Trex 700N is an aerobatic flying lawnmower, with no shield or guard to prevent you from hitting the blade. They are extremely dangerous and are not toys.
The octocopter's blades are much smaller and have way less momentum. Unless the octocopter hit you in the eye or fell from an extreme height, there's virtually no way to cause permanent damage with the octocopter. Many quad/octo copters have guards to prevent contact with the blade. A final version for the USPS might include some safety guards.
Note: I fly RC helicopters and planes.